Various types of thermometers have been used to measure a patient's temperature. Conventional types of thermometers include glass thermometers containing mercury, electronic probe thermometers for oral temperature measurement and tympanic infrared thermometers. This invention is particularly suited for use with electronic thermometers, especially those which measure tympanic membrane temperature via the ear canal.
FIG. 1 shows a side view of a typical hand-held electronic thermometer for tympanic membrane temperature measurement. A handle 10 connects to a housing 12 which contains the electronics. For details of the structure and operation of a conventional thermometer see, e.g., Wood, U.S. Pat. No. 4,895,164. The forward portion of the housing 12 includes a tube 15 having an opening 16 through which infrared radiation may be passed to the detection electronics (not shown). A probe cover 18 may be disposed over the tube 14. Generally, the probe cover comprises a window 20 through which the infrared radiation from the tympanic membrane may pass, and a side 22 which generally surrounds the tube 14. The interior portion of the side 22 may include a protrusion 24 which meets with a groove 26 to provide a minimal amount of locking force of the probe cover 18 onto the tube 14.
In operation, the user of the thermometer holds the handle 10 to support the thermometer. The tube 14, along with the probe cover 18, is placed at the ear of the patient and inserted pressure into the ear canal. The user then presses a read button 28 which causes the reading of the patient's temperature which is displayed on a display (not shown). After operation, an eject button 30 may be depressed which causes the probe cover 18 to be ejected.
The main function of the probe cover 18 is to prevent the spread of infection. Generally, the infection would be a cross infection from one patient to the next, though it is possible to reinfect a given patient, such as from one ear to the other, or by later reinsertion in the same ear.
Probe covers have taken various forms in the past. One form consists of a generally flat, generally infrared transmissive material surrounded by a collar or a ring. The collar or ring is disposed around the tube 14. The opening 16 of the tube 14 is then pressed through the infrared transmissive material, thereby expanding the material. These probe covers have suffered from tearing problems. Another conventional probe cover is that as shown in FIG. 1, generally comprising a cup shape. The cup may be formed of a single piece or multiple piece as desired. Generally, the cup is held on the thermometer by a friction fit. Supplemental restraining force may be provided by means such as the protrusion 24 and the groove 26.
A main deficiency of prior art designs is that it is possible to reuse the prove cover, especially the cup shaped probe cover. Such a reuse may happen unintentionally when a medical health professional comes upon a thermometer with a probe cover already on it. If there is no visible evidence of prior use, it may be assumed that the probe cover has not been used, when in fact it has been used. Similarly, under the press of rapidly changing events as often occurs in a hospital, the medical health professional may forget whether the probe cover has been changed. Additionally, while it is clearly counter to good medical practice, in an attempt to save costs, the probe cover may at times be reused.
The reuse of the probe cover presents several clear problems in the prior art. As described above, the problem of infection is clearly present from reuse of a probe cover. Additionally, the thermometer is calibrated for use of a probe cover which is at ambient temperature. In the event a probe cover is immediately reused, it may have a temperature above ambient temperature, thereby resulting in an inaccurate measurement of the patient's temperature.
Another problem well known to the prior art is the possibility of use of a thermometer without a probe cover. This may be done in order to save time or money, or both. This provides an even more severe problem with regard to infection. Additionally, it provides accuracy and repeatability problems in that the thermometers are calibrated to account for attenuation via absorption by the probe cover of the infrared radiation from the patient. If no probe cover is used, the reading is inaccurate because the thermometer attempts to account for a structure which is in fact not there.
Certain prior art thermometers have attempted to solve these problems by providing an external switch activated by the probe cover. However, this has not solved the problems in that the switch is external and easily overridden by the user if desired. These thermometers may additionally require the rejection of the probe cover prior to reactivation. However, there is nothing in this design which guarantees that a new probe cover must be used. In certain instances, the user may simply affix the previously used probe cover to the thermometer.
Yet another problem existing in the prior art designs is that the probe cover may remain in the patient's ear canal after removal of the thermometer. Since the fit between the probe cover and the tube 14 is basically a friction fit, when the friction between the probe cover and the ear canal is greater than that between the probe cover and the tube 14, the probe cover may remain within the ear canal. This results in lost time in the overall measurement and possible discomfort to the patient.
Despite these long standing and serious problems, no satisfactory solution has been advanced heretofore.